/Engine/Source/Runtime/Engine/Public/ImageUtils.h
Export Texture (2D,Array,Cube,CubeArray,Volume) to DDS reads from texture source, not platform data
static bool ExportTextureSourceToDDS ( TArray64< uint8 > & OutData, [UTexture](API\Runtime\Engine\Engine\UTexture) * Texture, int BlockIndex, int LayerIndex )